CCL:G: G gaussian calculation with freq=anharm

Pierre,
 Assuming you're using the VPT2 method built into G09, a total of 6N-11
 Hessian computations are required for a full anharmonic treatment of a
 nonlinear system. This would be 205 Hessians for your 36-atom molecule.
 The 6N-11 comes about due to the use of a two-sided finite difference
 approach to find the derivatives of the force constants with respect to
 displacements along each of the normal modes, plus one calculation for the
 unperturbed geometry: 2*(3N-6)+1 = 6N-12+1 = 6N-11.
 -Brian
 On Wed, Jul 6, 2016 at 12:00 PM, Pierre Archirel pierre.archirel*_*u-psud.fr
 <owner-chemistry : ccl.net> wrote:
 >
 > Sent to CCL by: "Pierre  Archirel" [pierre.archirel[]u-psud.fr]
 > Dear colleagues,
 > I am using gaussian 09 RevD01 with freq=anharm on a rather large molecule
 > (36 atoms) and the calculation has been now running for 150 hours on an 8
 > core machine. I am wondering if the total cpu time can be evaluated. I have
 > already got 100 DFT energies, is it possible to know the total number of
 > DFT calculations, to be done? Is it related to the 3n-6 degrees of freedom
 > of the molecule?
 > Many thanks in advnce,
 > Pierre Archirel
 > LCP, Orsay, France
 > pierre.archirel//u-psud.fr>
 >
 >